1. Field of the Invention
The present invention relates to a facsimile apparatus that makes connection to a communication destination according to SIS (Session Initiation Protocol) to perform facsimile communication with the communication destination via an IP network, and a control method therefor, as well as a storage device.
2. Description of the Related Art
Recently, with spread of the Internet and IP phones, a method for using an IP network as a communication route for facsimile communication is being established. At the same time, a protocol for performing call control for executing generation, change and disconnection of a session for real-time communication, such as SIP (Session Initiation Protocol) is being standardized. Furthermore, the T.38 protocol for converting a G3 facsimile (T.30) signal to an IP message on an IP network to perform real-time transmission is recommended (ITU-T Recommendation T.38).
A real-time type Internet facsimile apparatus performs real-time facsimile communication on an IP network using SIP and T.38. This real-time type Internet facsimile apparatus identifies the address of a communication destination by SIP first and determines what data is to be transmitted by what protocol in data transmission between a transmission source and a reception destination. For this real-time type Internet facsimile apparatus, SDP (Session Description Protocol) is used. Though the name SDP includes “Protocol”, it is actually what is obtained by formatting the form of describing media information. In the case of performing T.38 communication also, media classification of a session is used. The media classifications used are “image” or “application” in the case of T.38 communication, and “audio” in the case of voice communication (telephone call).
A conventional communication apparatus that performs communication control on the basis of communication destination information at the time of call connection by SIP obtains a call connection message from a communication destination apparatus in a predetermined call connection procedure performed prior to starting the T.38 communication. Then, the communication apparatus acquires communication destination attribute information as information indicating the attributes of the communication destination apparatus, from the obtained call connection message. Furthermore, such a communication apparatus is proposed that controls parameter values at the time of T.38 communication according to the acquired communication destination attribute information to control real-time type Internet facsimile communication (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2005-303968).
Equipment for performing SIP+T.38 communication includes a real-time type Internet facsimile apparatus, a T.38 GW or T.38 adapter, and there are multiple manufacturers that manufacture the equipment. Among the manufacturers or among models of the same manufacturer, there is difference in the adopted sequence for connection by the SIP protocol or difference in SDP description or the like accompanying difference in interpretation or function expansion.
Therefore, even between the same real-time type Internet facsimile apparatuses compatible with SIP+T.38 communication, a problem of connectivity or communicability, for example, a problem of communication sometimes being correctly performed and sometimes not being correctly performed may occur according to the manufacture or the model.